Lamp for vehicles.



l. M. CHATTERSGNU LAMP FOR VEHICLES. APPLICATION FiLED JULY 8.192s.

1,289Aifi1 Pasfielmted Siapt. 11, 191? IN VEIV TOR.

LAMP FOR VEHICLES.

Specification of Letters Patent.

Patented Sept. it, Mutt.

Application filed July 8, 1915. Serial No. 38,771.

To all whom it may concern:

Be 'it known that 1, James MARSHALL. CHAT'rnRsoN, a citizen of the United States, residing at San Diego, in the county of San Diego andState of California, have invented a new and useful Lamp for Vehicles, of which the following is a specification.

My invention relates to lamps for lighting the road before vehicles and the like, and some of the objects of my improvement are to utilize the maximum of the light radiated by the luminant by projecting it upon the roadway to be lighted, to illuminate a wide surface on the roadway and to either side thereof in order to facilitate turning out to either side without adjusting the lamp, to prevent the rays of light from dazzling and blinding the eyes of drivers of approaching vehicles, to accomplish this without the necessity of dimming or otherwise'adjusting the light, simplicity of construction and comparative cheapness of manufacture.

These and other objects I attain by means of the structure illustrated in the accompanying drawings, in which Figure l is a vertical, central section in perspective; and Fig. 2 is a horizontal section on the line A-B of Fig. 1.

Similar reference numbers refer to simi lar parts throughout the several views of the drawings.

The body of the lamp, which incloses the reflector and the luminant, is not shown in the drawings, since this may be of any shape that best suits the fancy of the manufacturer or user. The reflector, 1, is in the form of a parabolic cylinder, with the ends closed by plane, reflecting surfaces, 2 and 3. The upper limb of the parabola is preferably provided with a plane, horizontal extension, 4:, from 5 to 6, and the lower limb may have a forward and downwardsloping extension, 7, from 8 to 9. The upper part of the reflector is preferably formed longer. than the lower part, and the front opening is closed by a transparent cover or door, 10, which is placed at a suitable angle sloping backward toward the bottom of the lamp. The transparent door 10 is placed at such an angle that none of the rays from the luminant strike it at the critical angle or so as to be reflected.

The luminant comprises a straight, substantially linear incandescent filament, 11, or other substantially linear luminant, mounted in the focal "axisof the parabolic cylinder of the reflector. This I preferably attain by means of a tubular incandescent lamp, 12, having a straight, spiral tungsten filament extending axially from end to end provided with a terminal at each end. This linear luminant may be contemplated as comprising an infinite number of luminous points, and, being mounted in the focal axis of the parabolic cylinder, each of these points is located in the focus of the parabola. By this means, therefore, an intense illumination may be effected and almost wholly directed upon a desired area of the roadway, and the efficiency of the lamp is very great.

Referring now to Fig. 1, it will be seen that all those rays which strike the parabolic reflector, as 18, 1a, 15, 16, 17 are directed parallel and straight ahead, while those which strike the plane surface 4, as 18 and 19, are directed downward, at various angles, upon the roadway. Other rays, of those radiating forward and which miss the reflector entirely, as those in the angle between 20 and 21, radiate immediately downward upon the roadway, while those between 21 and 22 are the only rays which radiate upward and are liable to strike the eyes of an approaching driver. This last named section of the light is not sufficiently intense 'to blind or confuse the approaching driver, but is suflicient merely to indicate the position of the vehicle. This section of the light may be cut off or diminished by further extending the upper plane reflector, or by tilting the reflector downward.

By reference to Fig. 2, the direction of the rays which strike the lateral plane reflectors, 2 and 3, may be traced by keeping in mind the law that the angle of incidence and the angle of reflection are equal. It will now be understood that the light issu ing from my lamp .fallsupon the roadway in the form of a broad sheet, having its greatest intensity at the middle and diminishing on each side. Sufficient light is provided on the sides of the road to make them distinctly visible and sufficient on side streets to facilitate turning out without specially adjusting or turning the lamp relative to the vehicle. It will be seen that, with a good reflector, the maximum of the light produced at the luminant is available upon the roadway, where it is wanted, and the minimum is lost to the sky.

Furthermore, it is not necessary, to attain a definite focus, to confine the luminant to a point, and consequently limit the candle, power of the lamp, but any desired candle power may be obtained simply by extending the linear luminant, without disturbing the focus, and causing photo aberration. Nor is it found necessary to stop off stray rays, by means of diaphragms or other expedients or pass the rays through refracting media, to the loss of light, but the light is reflected directlyby simple reflecting surfaces and projected through thin, plane glass.

Having thus described my invention, so that anyone skilled in the art pertaining thereto may understand its construction and use, I claim 1. A lamp comprising a body, a luminant mounted in said body, a reflector mounted in-said body in the form of a parabolic cylinder with plane closed ends, and a plane reflecting extension on said cylinder.

2. An automobile headlight, comprising a reflector, generated by moving a relatively short straight line in a parabolic curve, the upper portion of said reflector being extended as a plane forwardly over the lower portion, mirrored surfaces closing said reflector on both sides, a downwardly and rearwardly extending transparent door closing the front, and a linear light source located in the focal axis of the reflector.

'J. MARSHALL CHATTERSON.

Witnesses:

ANNIE B. KNOBEL, MADELINE MILEY. 

